Conventionally, for example, in radio communication devices, such as base station devices or the like, due to aged deterioration of amplifiers in the devices or the like, the gain of the amplifiers may sometimes vary. Furthermore, in recent radio communication devices, studies have been conducted on a system in which a radio equipment control (REC) device that mainly performs a baseband process is connected, by using optical fibers, to radio equipment (RE) devices that mainly perform a radio process. The connection between the REC device and the RE devices is performed in accordance with, for example, an interface called a Common Public Radio Interface (CPRI).
In the radio communication devices, for example, because the gain prescribed by law is expected to be observed, in general, a periodic inspection is performed to determine whether the gain of an amplifier described above is within the range that satisfies the prescription. However, because the base station devices and the RE devices are often arranged at a high place, such as on the roof of a building, on a steel tower, or the like, the efficiency of checking the gain of the amplifiers in these devices by maintenance workers on site is low and the cost is increased.
Thus, studies have been conducted on various kinds of technologies in which a base station device or a RE device itself determines deterioration of an amplifier in the device. For example, it is conceivable to extract, in a device that has a distortion compensation function that compensates nonlinear distortion generated in an amplifier, a distortion compensation coefficient in accordance with a power value of the most frequently appearing radio signal, obtains an amount of variation in the distortion compensation coefficient that was extracted in the past, and determines, on the basis of the obtained amount of variation, the degradation of the amplifier.
Patent Document 1: Japanese Laid-open Patent Publication No. 2002-232305
However, if the degradation of the amplifier is determined by extracting the distortion compensation coefficient that is in accordance with the power value of the most frequently appearing radio signal, the frequency of appearance of the power value of the radio signal varies due to the location of the device that is placed or due to a use time zone of the device and thus the power value of the radio signal may possibly deviate from the nonlinear operation area of the amplifier. Here, when measuring variation of the gain that is used to determine the degradation of the amplifier, for example, it is prescribed by law that the power value of the radio signal needs to be present in a nonlinear operation area of the amplifier, i.e., it is prescribed by law that the power value of the radio signal needs to be equal to or greater than the threshold. Consequently, when the distortion compensation coefficient that is in accordance with the power value of the most frequently appearing radio signal is extracted, because the variation of the gain may possibly be measured by using the distortion compensation coefficient that is in accordance with the power value that does not satisfy the prescription of law, it is difficult to appropriately determine the degradation of the amplifier.